Mechanical coin discriminating devices are well known in the prior art. Such devices, however, are complicated in construction and are prone to erratic and unreliable operation. Though substantial improvements have been made in such devices over the years, their mechanical nature poses a severe limitation on their overall reliability and usefulness. One significant drawback to mechanical coin discriminating devices is that such devices cannot distinguish between real and counterfeit coins. Thus, substantial revenues are lost by vending machine operators due to the use of counterfeit coins by users.
An electromagnetic induction type coin discriminating device has been developed in order to overcome the problems of conventional coin discriminating devices mentioned above. One such device is disclosed in Japanese Patent Laid-Open Gazette No. 55-62350. This coin discriminating device has a coin sensor and circuitry for periodically activating the coin sensor. When a coin is positioned adjacent to the sensor coil, the device responds to a particular attenuation burst occurring on the sensor coil in order to sense the coin. The structure of the circuit, however, is complicated and thus the device is high in cost.